28281781 has 4 divisors (see below), whose sum is σ = 30852864. Its totient is φ = 25710700.

The previous prime is 28281779. The next prime is 28281791. The reversal of 28281781 is 18718282.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 28281781 - 2¹ = 28281779 is a prime.

It is a super-2 number, since 2×28281781² = 1599718273063922, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 28281781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28281731) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1285525 + ... + 1285546.

It is an arithmetic number, because the mean of its divisors is an integer number (7713216).

Almost surely, 2^28281781 is an apocalyptic number.

It is an amenable number.

28281781 is a deficient number, since it is larger than the sum of its proper divisors (2571083).

28281781 is a wasteful number, since it uses less digits than its factorization.

28281781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2571082.

The product of its digits is 14336, while the sum is 37.

The square root of 28281781 is about 5318.0617709839. The cubic root of 28281781 is about 304.6741337341.

The spelling of 28281781 in words is "twenty-eight million, two hundred eighty-one thousand, seven hundred eighty-one".